K+ currents of encephalitogenic memory T cells decrease with encephalitogenicity while interleukin-2 (IL-2) receptor expression remains stable during IL-2 dependent …

U Strauss, R Schubert, S Jung, E Mix - Receptors & channels, 1998 - europepmc.org
U Strauss, R Schubert, S Jung, E Mix
Receptors & channels, 1998europepmc.org
Previous studies revealed a linkage between increased K+ current and lymphocyte
activation upon non-specific stimulation with mitogenic lectins and antibodies. So far no
information is available about the behaviour of K+ currents in specifically autoantigen-
stimulated lymphocytes. Therefore, we have investigated K+ currents in encephalitogenic T
line cells, specifically stimulated with myelin basic protein, using the whole-cell patch-clamp
technique. In parallel, the T cell activation marker interleukin-2 (IL-2) receptor was measured …
Previous studies revealed a linkage between increased K+ current and lymphocyte activation upon non-specific stimulation with mitogenic lectins and antibodies. So far no information is available about the behaviour of K+ currents in specifically autoantigen-stimulated lymphocytes. Therefore, we have investigated K+ currents in encephalitogenic T line cells, specifically stimulated with myelin basic protein, using the whole-cell patch-clamp technique. In parallel, the T cell activation marker interleukin-2 (IL-2) receptor was measured quantitatively by flow cytometry. Outward currents were observed in response to depolarizing voltage steps from a holding potential of-80mV. The peak current density increased with more positive membrane potentials, where the current threshold was about-40mV and the maximum conductance was 1.22 nS/pF. This current was characterized by a fast activation and a fast inactivation with half maximal inactivation at-67mV. The sensitivity of the peak current to K+ channel blocking agents was as follows: 4-aminopyridine (4-AP) had a half blocking concentration of 0.4 mM and a maximal block of 83.7% at 10mM 4-AP, tetraethyl-ammonium caused a block of 6% at 0.1 mM, 15% at 1mM and 40% at 10mM, charybdotoxin blocked 90% at 100nM, whereas iberiotoxin had no effect (all values at a clamped membrane potential of+ 30mV). The encephalitogenic T cells used in our study reach their highest encephalitogenic potency on day 3 to 4 after the onset of restimulation. Furthermore, K+ currents were measured during the whole course of an in vitro restimulation cycle. The peak currents normalized to cell capacitance reached their maximum on day 2 (326+/-52.8 pA/pF, n= 4) and decreased thereafter as follows: day 3: 139.7+/-7.87 pA/pF (n= 27), day 4: 85.4+/-8.95 pA/pF (n= 28) and day 5: 40.9+/-7.45 pA/pF (n= 17). The activation and inactivation characteristics of the current and its responses to selective blockers were similar at all days after restimulation. In contrast to the K+ current, IL-2 receptor expression was maintained on> 95% of cells until day 6 after restimulation. In conclusion, the K+ currents measured in rat encephalitogenic T cells resemble n-type voltage-gated K+ currents described in mice and man. The comparison of K+ current, IL-2 receptor expression and encephalitogenic potency let us suppose that the observed K+ current represents an early event of specific T cell activation and can serve as a parameter of high functional activity of T cells corresponding to their encephalitogenicity.
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